Polyester is a category o polymers that conteen the ester functional group in their main chain. As a speceefic material, it maist commonly refers tae a teep cried polyethylene terephthalate (PET). Polyesters include naiturally occurrin chemicals, such as in the cutin o plant cuticles, as well as seenthetics throu step-growth polymerisation such as polybutyrate. Naitural polyesters an a few seenthetic anes are biodegradable, but maist synthetic polyesters are nae. This material is uised very widely in cleidin.